Databases use an Application Programming Interface (API) to provide a standardized way for applications, written in general-purpose languages like Java or Python, to communicate with them. APIs such as Java Database Connectivity (JDBC) or Open Database Connectivity (ODBC) define a set of functions and protocols that allow a program to connect to the database, submit SQL queries as text strings, and retrieve the results in a structured format. This abstracts the low-level complexity of network communication and internal database operations, thereby simplifying the integration of SQL into application code.

A. The storage manager is an internal database component that interacts with the file system; it is not an interface for application developers.

B. The ability to reverse results (transaction rollback) is a feature of transaction management, not the primary mechanism for integrating SQL with a language.

C. The query processor is an internal engine that executes queries; the API is the external interface that applications use to submit queries to this processor.

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1. Silberschatz, A., Korth, H. F., & Sudarshan, S. (2020). Database System Concepts (7th ed.). McGraw-Hill. In Chapter 4, "Advanced SQL," Section 4.1, "Accessing SQL From a Programming Language," it states, "An application program that needs to access a database can use an application programming interface (API) to communicate with the database. The two main standards for database APIs are ODBC and JDBC." (p. 131).

2. Oracle Corporation. (2023). JDBC Developer's Guide, 23c. In the "Introduction to JDBC" section, it is stated: "The JDBC API is a Java API that enables Java programs to execute SQL statements... With the JDBC API, you can write applications that manage these tasks: Connecting to a data source, such as a database; Sending queries and update statements to the database; Retrieving and processing the results received from the database in answer to your query."

3. Ullman, J. D., & Widom, J. (n.d.). CS145 Introduction to Databases, Lecture Notes: SQL in Applications. Stanford University. The notes on JDBC describe it as "an API for database access from Java" and detail the process of establishing a connection, creating statements, and executing queries, which exemplifies the role of an API in bridging the application and the database.